Due to insufficient financial support and unceasing work, the rural elderly in China experience a range of mental disorders, and the most common one is depression. This study aims to investigate the association between public pension, labor force participation (LFP), and depressive symptoms for older men and women in rural China. A moderated mediation analysis is conducted using data in the 2015 wave extracted from the China Health and Retirement Longitudinal Study (CHARLS), a continuous national social survey. A total of 2709 available surveys were obtained in our analysis. Using PROCESS, results revealed that the income from China’s New Rural Pension Scheme (NRPS) was directly negatively related to depressive symptoms. However, LFP did not mediate the link between pension income (PI) and depressive symptoms in the total study population. The results of moderated mediation estimates indicated that gender significantly moderated the relationship between LFP and depressive symptoms. Specifically, for older women, the indirect effect of PI on depressive symptoms via LFP was significant, but not for the opposite sex. In order to improve the mental health of older adults in rural China, the policy makers and mental health therapists need to pay attention to the aforementioned factors.

The modular multilevel AC/AC converter topology in Y configuration, which is called Y‐MMC, suitable for fractional frequency transmission system is proposed in this paper. Y‐MMC can directly connect two three‐phase AC systems of different frequencies and voltage amplitudes with only six equivalent branches, and it has satisfying performance in power quality and characteristics. Y‐MMC enjoys a simple and symmetrical structure with no circulating current problem. The detailed topology and operating principle of Y‐MMC are addressed in this paper. The frequency‐decoupled mathematical model of the Y‐MMC system is deduced. Corresponding control scheme is thoroughly designed, including the inner loop current control, the outer loop control, the individual‐balancing control, and frequency leakage suppression control. The paper also lays emphasis on the optimization of reactive power distribution between the main branches and the assistant branches of Y‐MMC. The validity of the Y‐MMC topology and the effectiveness of the proposed control scheme are verified by the simulation results in MATLAB/Simulink. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

We present a laser machining method for fabricating an all-fiber pillar-in-bubble Fabry-Perot interferometer (FPI), which is used for strain sensors with high sensitivity. The micro-structure of the air-bubble is fully controllable, especially the cavity length and sidewall thickness. The measured sensitivity of this strain sensor is as high as 56.69 pm/με, which is several times higher than that of most FPI strain sensors reported to date. This sensor also has a low-temperature sensitivity of 0.682 pm/°C, reducing the cross-sensitivity between tensile strain and temperature to 0.012 με/°C. Furthermore, such a sensor has the benefits of flexible design, simple fabrication, and high reproducibility, making it attractive for practical applications.

We demonstrate an active acoustic sensor based on a high-finesse fiber Fabry–Pérot micro-cavity with a gain medium. The sensor is a compacted device lasing around 1535 nm by external optical pumping. The acoustic pressure acting on the sensor disturbs the emitted laser frequency, which is subsequently transformed to beat signals through a delay-arm interferometer, and directly detected by a photo-detector. In this configuration, the sensing device exhibits a high sensitivity of 2.6 V/Pa and a noise equivalent acoustic signal level of 230 μPa/Hz1/2 at a frequency of 4 kHz. Experimental results provide a wide frequency response from 100 Hz to 18 kHz. As the sensor works at communication wavelength and the output laser can be electrically tuned in the 10 nm range, a multi-sensor network can be easily constructed with the dense wavelength division multiplexing devices. Extra lasers or demodulators are unnecessary thus the proposed sensor is low cost and easy fabrication. The proposed sensor shows broad applications prospect in remote oil and gas leakage exploration, photo-acoustic spectrum detection, and sound source location.

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